At present it is very difficult to form such a surface in such a way as to have the axis of the surface of revolution, obtained by a mechanical machining at or in the end of the body, coincident with a predetermined longitudinal axis of said body.
Consider, for example, the case in which a tapered cavity is obtained by a turning operation on a ferrule provided with a through hole, so that the axes of the taper cavity and of the through hole coincide, one with the other, by affixing said ferrule in a projecting manner on a mandrel placed at the end of a shaft of a lathe and forming said cavity by means of the action of a suitable tool.
The securing of a body, such as, for example, a ferrule, on a mandrel placed at the end of an unavoidably flexible rotating shaft, causes oscillations of the end of the body in a plane perpendicular to the axis of the ferrule, and the cutting action of the tool intensifies said oscillations.
Therefore, unless a machine tool of great cost is used, the ferrule is positioned with great precision in the mandrel and the cutting of said tapered cavity proceeds very slowly to reduce to the minimum the oscillations of the ferrule, the axis of the tapered cavity is more or less out of alignment with respect to the axis of the through cylindrical hole.
This misalignment leads, in the particular case of the ferrule of the type in question, to a reduction or to a direction deflection of the signal transmitted which sometimes can be intolerable.
One object of the present invention is that of eliminating or at least reducing sufficiently the perpendicular oscillations of any predetermined axis of a body to enable the axis of the surface of revolution produced at one end of said body to get near to and to line up as much as possible with the said predetermined axis of said body without making use of particularly precise and expensive machine tools.
In the particular case of the ferrules to which, from now on, reference will be mainly made, although it is to be understood that the present invention has other applications, it has to be stated beforehand that, owing to the very reduced diameter, of the order of a tenth of a millimeter (the typical diameter is of 125 microns), said hole cannot be obtained by means of a common drilling technique. Instead, it is obtained by forming said body or ferrule by means of a material consolidatable around a filiform core substantially of the same diameter as the through hole which it is desired to obtain, the filiform core being subsequently removed, such as by chemical means.
Therefore, it will be understood why it is difficult to subsequently align the axis of a tapered cavity with that of the through hole.